Mills was originally a boomtown that sprang up in 1919 following construction of the Midwest Refining Company, located across the North Platte River. The Mills Construction Company bought the entire section for the purpose of mining gravel with which to construct roads and tank revetments. Company employees purchased lots and built makeshift houses. The town was mostly comprised of tarpaper shacks, with one block of permanent houses, a hotel, and an amusement park. By 1921, the town had 1,000 residents and was officially incorporated. When the refinery construction was complete and the depression began, Mills nearly became a ghost town. The Mills Hotel, when demolished in 1931, was described as follows: “It started out in resplendent fashion, a smart hotel hurriedly erected to care for the hordes in pursuit of their fortune. It ran the gamut of open handed patronage, gamblers, surging throngs, beautiful women – a slice as it were, of the frenzied boom period, becoming in later years, its feathers bedraggled, a speakeasy, dancing hall, gambling den. Then oblivion.” Mills benefited from a healthy local economy in the 1950s and the construction of a bridge connecting with the Fort Caspar area made transportation easier. The 1970s boom and mid-1980s bust affected Mills as it did the rest of Natrona County. As the rest of the state, Mills is currently benefiting from renewed economic activity.

Several organizations are working to preserve the area’s history. They include the Natrona County Historical Society, the Oregon-California Trails Association, the Fort Caspar Museum Association, the Natrona County, Casper, and Mills Preservation Commissions, and the Casper College Western History Center.